Pressure-sensitive adhesive composition

ABSTRACT

Provided are a pressure-sensitive adhesive composition, an encapsulation film including the same, an organic electronic device including the same, and a method of manufacturing the organic electronic device. Therefore, provided is the pressure-sensitive adhesive composition, which can form a structure capable of effectively blocking moisture or water entering the organic electronic device from the outside, and have excellent processability in a process of manufacturing a panel and excellent heat retention under a high-temperature and high-humidity condition.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.2015-0017620, filed on Feb. 4, 2015 with the Korean IntellectualProperty Office, the disclosure of which is herein incorporated byreference in its entirety.

BACKGROUND

1. Field of the Invention

The present application relates to a pressure-sensitive adhesivecomposition, an encapsulation film including the same, an organicelectronic device (OED) including the same, and a method ofmanufacturing an OED using the same.

2. Discussion of Related Art

An OED is a device including an organic material layer in which electriccharges are exchanged using holes and electrons, and the OED may be, forexample, a photovoltaic device, a rectifier, a transmitter, or anorganic light emitting diode (OLED).

Among the OEDs, an OLED has a lower power consumption and a higherresponse speed, and is advantageous to a thinner display device orlighting than a conventional light source. Such an OLED also hasexcellent space applicability, and is expected to be applied to variousfields including all kinds of portable devices, monitors, notebookcomputers and TVs.

For commercialization and expanded use of the OLED, the most criticalproblem is durability. Organic materials and metal electrodes includedin the OLED are very easily oxidized by an external factor, for example,moisture. Therefore, a product including an OLED is very sensitive toenvironmental factors. For this reason, various methods have beensuggested to effectively prevent the permeation of oxygen or moistureinto an OED such as an OLED from the outside.

In Patent Document 1, an adhesive capsulation composition film and anorganic electroluminescent element are disclosed, and the composition isa polyisobutylene (PIB)-based pressure-sensitive adhesive, but has lowprocessability and low reliability under a high-temperature andhigh-humidity condition. In addition, in a process of laminatinglarge-scale flat panels, air bubbles are enclosed between the panels,and therefore a uniform laminating property may not be obtained.

Therefore, there is a demand for developing an encapsulant, which allowsan OED to ensure a demanded lifespan, effectively prevents thepermeation of moisture into the OED, maintains reliability under ahigh-temperature and high-humidity condition, and has an excellentlaminating property, which is one of the characteristics required duringa process of manufacturing a panel.

PRIOR ART Patent Document

(Patent Document 1) Korean Unexamined Patent Application Publication No.2008-0088606

SUMMARY OF THE INVENTION

The present application provides a pressure-sensitive adhesivecomposition which can form a structure capable of effectively blockingmoisture or oxygen entering an OED from the outside, has excellentprocessability during a process of manufacturing a panel and excellentheat retention under a high-temperature and high-humidity condition, andan encapsulation film.

Hereinafter, with reference to the accompanying drawings, exemplaryembodiments of the present application will be described in furtherdetail. In addition, to explain the present application, detaileddescriptions for known general functions or configurations will beomitted. In addition, the accompanying drawings are schematicallyprovided to help in understanding the present application. To moreclearly explain the present application, parts not relating to theexplanation will be omitted, thicknesses are exaggerated to clearlyexpress several layers and regions. The scope of the present applicationis not limited by thicknesses, sizes, and ratios shown in the drawings.

The present application relates to a pressure-sensitive adhesivecomposition. The pressure-sensitive adhesive composition may be appliedto encapsulate or capsulate an OED such as an OLED.

The term “organic electronic device (OED)” used herein is a product ordevice having a structure including an organic material layer in whichelectric charges are exchanged using holes and electrons between a pairof electrodes facing each other, and examples of the OED may include,but the present application is not limited to, a photovoltaic device, arectifier, a transmitter, and an OLED. In an exemplary embodiment of thepresent application, the OED may be an OLED.

The pressure-sensitive adhesive composition of the present applicationmay be formed in an encapsulation film, for example, which seals theentire surfaces of an organic electronic element of the OED so as toprotect the element from moisture or oxygen. Such a pressure-sensitiveadhesive composition may include a polymer derived from butylene and acompound satisfying Formula 1 shown below. The compound of Formula 1 mayinclude a monofunctional acrylate.

In Formula 1, T may be a linear or branched alkyl group, alkenyl groupor alkynyl group. The alkyl, alkenyl group or alkynyl group may have alinear or branched structure having 6 to 30, 7 to 25, 8 to 23, 9 to 20,10 to 19, 6 to 17 or 6 to 11 carbon atoms. Also, T may be—U—[O—W]_(n)—O-Q. Here, U and W are each independently an alkylene groupor alkylidene group, and Q is an alkyl group, alkenyl group, alkynylgroup or aryl group. Also, n is a number from 0 to 10, and when n is 0,U may be directly linked to —O-Q. Since the pressure-sensitive adhesivecomposition of the present application includes both of a hydrophobicpolymer and the specific compound of Formula 1, when applied toencapsulation of the organic electronic element, the composition canexhibit excellent processability during the process of manufacturing apanel and excellent heat retention under a high-temperature andhigh-humidity condition.

In an exemplary embodiment, the composition may include 60 to 95 partsby weight of the polymer derived from butylene and 5 to 40 parts byweight of the compound satisfying Formula 1. In an exemplary embodiment,the composition may include 60 to 90 parts by weight of the polymerderived from butylene and 10 to 40 parts by weight of the compoundsatisfying Formula 1, or 65 to 90 parts by weight of the polymer derivedfrom butylene and 10 to 35 parts by weight of the compound satisfyingFormula 1. In the present application, as the contents of the componentsare adjusted in the above-described ranges, an excellent moistureblocking property and heat retention under a high-temperature andhigh-humidity condition may be realized. The compound of Formula 1 mayinclude, but is not particularly limited to, n-octyl acrylate, iso-octylacrylate, iso-nonyl acrylate, lauryl acrylate, stearyl acrylate,isostearyl acrylate, isodecyl acrylate, 2-(2-ethoxyethoxy)ethylacrylate, methoxytriethyleneglycol acrylate, ormethoxypolyethyleneglycol acrylate.

The term “alkyl group” used herein may be, unless particularly definedotherwise, an alkyl group having 1 to 30, 1 to 25, 1 to 20, 1 to 16, 1to 12, 1 to 8, or 1 to 4 carbon atoms. The alkyl group may have alinear, branched or cyclic structure, and may be arbitrarily substitutedwith at least one substituent.

Also, the term “alkenyl group” or “alkynyl group” used herein may be,unless particularly defined otherwise, an alkenyl or alkynyl grouphaving 2 to 20, 2 to 16, 2 to 12, 2 to 8, or 2 to 4 carbon atoms. Thealkenyl or alkynyl group may be linear, branched or cyclic. Also, thealkenyl group may be arbitrarily substituted with at least onesubstituent.

Also, the term “alkylene group” or “alkylidene group” used herein maybe, unless particularly defined otherwise, an alkylene or alkylidenegroup having 2 to 30, 2 to 25, 2 to 20, 2 to 16, 2 to 12, 2 to 10, or 2to 8 carbon groups. The alkylene group or an alkylidene group may belinear, branched or cyclic. Also, the alkylene or alkylidene group maybe arbitrarily substituted with at least one substituent.

The term “aryl group” used herein may be, unless particularly definedotherwise, a monovalent residue derived from a compound including astructure in which benzene is included or two or more benzenes arecondensed or coupled, or a derivative thereof. The aryl group may have 6to 22, preferably 6 to 16, and more preferably 6 to 13 carbon atoms, andmay be, for example, a phenyl group, a phenylethyl group, a phenylpropylgroup, a benzyl group, a tolyl group, a xylyl group or a naphthyl group.

The term “polymer derived from butylene” may mean that one or morepolymerization units of the polymer are derived from butylene. Since thepolymer derived from butylene has a very low polarity, is transparentand almost has no influence of corrosion, when used as an encapsulant orsealant, the polymer may exhibit an excellent moisture blocking propertyand durability and reliability.

In the present application, also, the polymer derived from butylene maybe a homopolymer of a butylene monomer; a copolymer formed bycopolymerizing a butylene monomer with a different polymerizablemonomer; a reactive oligomer using a butylene monomer; or a mixturethereof. The polymer derived in the present application refers that apolymer is formed with a unit of polymerized monomers. The butylenemonomer may include, for example, 1-butene, 2-butene or isobutylene.

The butylene monomer or the different monomer capable of beingpolymerized with a derivative may include, for example, isoprene,styrene or butadiene. When the copolymer is used, physical propertiessuch as processability and a crosslinking degree may be maintained, andtherefore, when applied to the OED, thermal resistance of thepressure-sensitive adhesive itself may be ensured.

Also, the reactive oligomer using a butylene monomer may include abutylene polymer having a reactive functional group. The oligomer mayhave a weight average molecular weight of 500 to 5000. Also, thebutylene polymer may be linked to a different polymer having a reactivefunctional group. The different polymer may be an alkyl (meth)acrylate,but the present application is not limited thereto. The reactivefunctional group may be a hydroxyl group, a carboxyl group, anisocyanate group or a nitrogen-containing group. Also, the reactiveoligomer and the different polymer may be crosslinked by amultifunctional crosslinking agent, which may be one or more selectedfrom the group consisting of an isocyanate crosslinking agent, an epoxycrosslinking agent, an aziridine crosslinking agent and a metal chelatecrosslinking agent.

In an exemplary embodiment, the polymer derived from butylene of thepresent application may be a copolymer of diene and an olefin-basedcompound including one carbon-carbon double bond. Here, the olefin-basedcompound may include butylene, and the diene may be a monomer capable ofbeing polymerized with the olefin-based compound, for example, isopreneor butadiene. For example, the copolymer of the olefin-based compoundincluding a carbon-carbon double bond and diene may be butyl rubber.

In the present application, the polymer may have a certain weightaverage molecular weight (MW) so that a pressure-sensitive adhesivecomposition can be molded in a film shape. For example, the polymer mayhave a weight average molecular weight of about 10,000 to 2,000,000,10,000 to 1,000,000, 10,000 to 500,000 or 10,000 to 300,000. In thepresent application, the term “weight average molecular weight” is avalue converted with respect to standard polystyrene measured by gelpermeation chromatography (GPC). However, the above-described weightaverage molecular weight does not necessarily have a resin component.For example, even when the molecular weight of the resin component isnot enough to form a film, a separate binder resin may be blended in thepressure-sensitive adhesive composition. The term polymer and the resincomponent may have the same meaning as each other.

In an exemplary example of the present application, thepressure-sensitive adhesive composition may further include amultifunctional active energy ray polymerizable compound, which can bepolymerized by irradiation with an active energy ray. The active energyray polymerizable compound may satisfy Formula 2.

In Formula 2, R₁ is hydrogen or an alkyl group having 1 to 4 carbonatoms, n is an integer of 2 or higher, and X is a residue derived from alinear, branched or cyclic alkyl group having 3 to 30 carbon atoms.

The active energy ray polymerizable compound satisfying Formula 2particularly has an excellent compatibility with the polymer of thepresent application, and therefore can satisfy reliability under ahigh-temperature and high-humidity condition. For example, the activeenergy ray polymerizable compound may realize a pressure-sensitiveadhesive composition having an excellent moisture blocking property andexcellent reliability under a high-temperature and high-humiditycondition, along with the above-described polymer derived from butylene.

The active energy ray polymerizable compound may refer to a compoundincluding two or more functional groups capable of participating in apolymerization reaction by irradiation with an active energy ray, forexample, functional groups including an ethylene-like unsaturated doublebond such as an acryloyl or methacryloyl group, and functional groupssuch as an epoxy or oxetane group.

As described above, the active energy ray polymerizable compound maysatisfy Formula 2 as follows.

In Formula 2, R₁ is hydrogen or an alkyl group having 1 to 4 carbonatoms, n is an integer of 2 or higher, and X is a residue derived from alinear, branched or cyclic alkyl group having 3 to 30 carbon atoms.Here, when X is a residue derived from a cyclic alkyl group, X may be aresidue derived from a cyclic alkyl group having 3 to 30, 6 to 28, 8 to22, or 12 to 20 carbon atoms. Also, when X is a residue derived from alinear alkyl group, X may be a residue derived from a linear alkyl grouphaving 3 to 30, 6 to 25, or 8 to 20 carbon atoms. Also, when X is aresidue derived from a branched alkyl group, X may be a residue derivedfrom a branched alkyl group having 3 to 30, 5 to 25, or 6 to 20 carbonatoms.

The term “residue derived from an alkyl group” used herein may refer toa residue of a specific compound, for example, an alkyl group. In oneexample, in Formula 2, when n is 2, X may be an alkylene group. Also,when n is 3 or higher, two or more hydrogens are released from an alkylgroup of X, and may be bound to a (meth)acryloyl group of Formula 2.

The multifunctional active energy ray polymerizable compound capable ofbeing polymerized by the radiation of an active energy ray may be usedwithout limitation as long as satisfying Formula 2. For example, thecompound may be 1,4-butanediol di(meth)acrylate, 1,3-butylene glycoldi(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,8-octanedioldi(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, neopentyl glycoldi(meth)acrylate, dicyclopentanyl di(meth)acrylate,cyclohexane-1,4-dimethanol di(meth)acrylate, tricyclodecane dimethanol(meth)diacrylate, dimethylol dicyclopentane di(meth)acrylate, neopentylglycol-modified trimethylpropane di(meth)acrylate, adamantanedi(meth)acrylate, trimethylolpropane tri(meth)acrylate, or a mixturethereof.

As the multifunctional active energy ray polymerizable compound, forexample, a compound having a molecular weight of less than 1,000 andincluding two or more functional groups may be used. In this case, themolecular weight may refer to a weight average molecular weight or aconventional molecular weight. A ring structure included in themultifunctional active energy ray polymerizable compound may be any oneof a carbocyclic structure, a heterocyclic structure, a monocyclicstructure or a multicyclic structure.

In an exemplary embodiment, the composition may include 50 to 90 partsby weight of the polymer derived from butylene, 5 to 35 parts by weightof the compound satisfying Formula 1, and 5 to 25 parts by weight of themultifunctional active energy ray polymerizable compound of Formula 2.In an exemplary embodiment, the pressure-sensitive adhesive compositionmay include the polymer derived from butylene, the compound satisfyingFormula 1 and the multifunctional active energy ray polymerizablecompound of Formula 2 in a weight ratio of 50 to 85 parts by weight, 5to 30 parts by weight and 10 to 25 parts by weight; or 60 to 85 parts byweight, 10 to 30 parts by weight and 2 to 20 parts by weight,respectively. In the present application, as the contents of thecomponents are adjusted in the above ranges, an excellent moistureblocking property and heat retention under a high-temperature andhigh-humidity condition may be realized.

In an exemplary embodiment, the pressure-sensitive adhesive compositionmay further include a tackifier, which is preferably a hydrogenatedcyclic olefin-based polymer. As the tackifier, for example, ahydrogenated petroleum resin obtained by hydrogenating a petroleum resinmay be used. The hydrogenated petroleum resin may be partially orcompletely hydrogenated, or a mixture of such resins may be used. Forthe tackifier, one having a high compatibility with a pressure-sensitiveadhesive composition, an excellent moisture blocking property, and a lowcontent of an organic volatile component may be selected. As a specificexample of the hydrogenated petroleum resin, a hydrogenatedterpene-based resin, a hydrogenated ester-based resin or a hydrogenateddicyclopentadiene-based resin may be used. A weight average molecularweight of the tackifier may be about 200 to 5,000. The content of thetackifier may be suitably adjusted as necessary. For example, a contentof the tackifier may be selected by considering the compatibility with apolymer, and according to an example, based on 100 parts by weight ofthe polymer, the tackifier may be included at 5 to 100 parts by weight,8 to 95 parts by weight, 10 to 93 parts by weight or 15 to 90 parts byweight.

In an exemplary embodiment of the present application, thepressure-sensitive adhesive composition may further include a radicalinitiator capable of inducing the polymerization reaction of theabove-described active energy ray polymerizable compound. The radicalinitiator may be a photoinitiator or thermal initiator. A specific typeof the photoinitiator may be suitably selected by considering a curingrate and yellowing probability. For example, a benzoin-based, hydroxyketone-based, amino ketone-based or phosphine oxide-based photoinitiatormay be used, and specifically, benzoin, benzoin methylether, benzoinethylether, benzoin isopropylether, benzoin n-butylether, benzoinisobutylether, acetophenone, dimethylamino acetophenone,2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone,2-hydroxy-2-methyl-1-phenylpropane-1-one, 1-hydroxycyclohexylphenylketone,2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propane-1-one,4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)ketone, benzophenone,p-phenylbenzophenone, 4,4′-diethylaminobenzophenone,dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone,2-t-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone,2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone,2,4-diethylthioxanthone, benzyldimethylketal, acetophenonedimethylketal, p-dimethylamino benzoic acid ester,oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone] or2,4,6-trimethylbenzoyl-diphenyl-phosphineoxide may be used.

The radical initiator may be included at 0.2 to 20 parts by weight, 0.5to 18 parts by weight, 1 to 15 parts by weight, or 2 to 13 parts byweight with respect to 100 parts by weight of the active energy raypolymerizable compound. Therefore, a reaction of the active energy raypolymerizable compound may be effectively induced, and degradation ofthe physical properties of the pressure-sensitive adhesive compositiondue to a component remaining after curing may be prevented.

The pressure-sensitive adhesive composition may further include amoisture scavenger when needed. The term “moisture scavenger” may referto a material capable of removing moisture or vapor permeated into anencapsulation film that will be described later by a chemical reactiontherewith. Specifically, the pressure-sensitive adhesive composition maybe applied to encapsulate an OED, when formed in a film.

For example, the moisture scavenger may be present to be uniformlydispersed in the pressure-sensitive adhesive composition or apressure-sensitive adhesive layer that will be described later. Here,the uniformly dispersed state may mean a state in which the moisturescavenger is present even in any part of the pressure-sensitive adhesivecomposition or the pressure-sensitive adhesive layer at the same orsubstantially the same density. As the moisture scavenger, for example,a metal oxide, a sulfate or an organic metal oxide may be used.Specifically, as an example of the sulfate, magnesium sulfate, sodiumsulfate or nickel sulfate may be used, and as an example of the organicmetal oxide, aluminum oxide octylate may be used. Here, a specificexample of the metal oxide may be phosphorous pentoxide (P₂O₅), lithiumoxide (Li₂O), sodium oxide (Na₂O), barium oxide (BaO), calcium oxide(CaO) or magnesium oxide (MgO), and an example of the metal salt may bea sulfate such as lithium sulfate (Li₂SO₄), sodium sulfate (Na₂SO₄),calcium sulfate (CaSO₄), magnesium sulfate (MgSO₄), cobalt sulfate(CoSO₄), gallium sulfate (Ga₂(SO₄)₃), titanium sulfate (Ti(SO₄)₂) ornickel sulfate (NiSO₄), or a metal halide such as calcium chloride(CaCl₂), magnesium chloride (MgCl₂), strontium chloride (SrCl₂), yttriumchloride (YCl₃), copper chloride (CuCl₂), cesium fluoride (CsF),tantalum fluoride (TaF₅), niobium fluoride (NbF₅), lithium bromide(LiBr), calcium bromide (CaBr₂), cesium bromide (CeBr₃), seleniumbromide (SeBr₄), vanadium bromide (VBr₃), magnesium bromide (MgBr₂),barium iodide (BaI₂) or magnesium iodide (MgI₂); or a metal chloratesuch as barium perchloride (Ba(ClO₄)₂) or magnesium perchloride(Mg(ClO₄)₂), but the present application is not limited thereto. As themoisture scavenger that can be included in the pressure-sensitiveadhesive composition, one or two or more of the above-describedcomponents may be used. In an exemplary embodiment, when the two or moreof the above-described components are used as the moisture scavenger,calcined dolomite may be used.

Such a moisture scavenger may be controlled in a suitable size accordingto use. In an exemplary embodiment, an average particle size of themoisture scavenger may be controlled to about 10 to 15000 nm. Themoisture scavenger having a size in the above range may be easily storedsince a reaction speed of the moisture scavenger with moisture is not sofast, and effectively remove moisture without damage to an element to beencapsulated.

A content of the moisture scavenger may be suitably selected byconsidering a desired blocking property without particular limitation.

The pressure-sensitive adhesive composition may also include a moistureblocker when needed. The term “moisture blocker” used herein may be amaterial that has no reactivity with moisture or can prevent orinterfere with the movement of moisture or vapor in a film. As themoisture blocker, one or two or more of clay, talc, needle-like silica,plate-like silica, porous silica, zeolite, titania and zirconia may beused. Also, a surface of the moisture blocker may be treated with anorganic modifier to facilitate penetration of an organic material. Suchan organic modifier may be, for example, dimethyl benzyl hydrogenatedtallow quaternary ammonium, dimethyl hydrogenated tallow quaternaryammonium, methyl tallow bis-2-hydroxyethyl quaternary ammonium, dimethylhydrogenated tallow 2-ethylhexyl quaternary ammonium, dimethyldehydrogenated tallow quaternary ammonium or a mixture thereof.

A content of the moisture blocker may be suitably selected byconsidering a desired blocking property without particular limitation.

In addition to the above-described components, various additives may beincluded in the pressure-sensitive adhesive composition according to itsuse and process of manufacturing a pressure-sensitive adhesive film thatwill be described later. For example, the pressure-sensitive adhesivecomposition may include a curable material, a crosslinking agent, or afiller in a suitable range of content according to a desired physicalproperty.

The present application also relates to an encapsulation film. Theencapsulation film may include the above-described pressure-sensitiveadhesive composition or a pressure-sensitive adhesive layer including acrosslinked product thereof.

In an exemplary embodiment, the pressure-sensitive adhesive layer mayhave a single layer structure or multilayer structure having two or morelayers. When the pressure-sensitive adhesive layer is formed with two ormore layers, the composition of each layer of the pressure-sensitiveadhesive layer may be the same as or different from each other. Forexample, the encapsulation film may include a second layer including theabove-described pressure-sensitive adhesive layer and a first layerincluding a pressure-sensitive adhesive resin or adhesive resin. Thepressure-sensitive adhesive resin included in the first layer may be thesame as or different from the above-described polymer, and may besuitably selected by a purpose of those of ordinary skill in the art.Also, each of the first and second layers may or may not include themoisture scavenger.

In an exemplary embodiment, the adhesive resin included in the firstlayer may be cured to have an adhesive property, and may include acurable resin having one or more thermally-curable functional groupssuch as a glycidyl group, an isocyanate group, a hydroxyl group, acarboxyl group or an amide group, or one or more functional groupscapable of being cured by irradiation with electromagnetic waves, forexample, an epoxide group, a cyclic ether group, a sulfide group, anacetal group or a lactone group. Also, a specific type of the resin maybe, but is not limited to, an acryl resin, a polyester resin, anisocyanate resin or an epoxy resin.

In the present application, as the curable resin, an aromatic oraliphatic epoxy resin; or a linear or branched epoxy resin may be used.In an exemplary embodiment of the present application, the curable resincontaining two or more functional groups may be an epoxy resin having anepoxy equivalent of 180 to 1,000 g/eq. By using the epoxy resin havingthe above range of equivalent, properties such as an adhesionperformance and a glass transition temperature of a cured product may beeffectively maintained. As an example of the epoxy resin, one of acresol novolac epoxy resin, a bisphenol A-type epoxy resin, a bisphenolA-type novolac epoxy resin, a phenol novolac epoxy resin, atetrafunctional epoxy resin, a biphenyl-type epoxy resin, a triphenolmethane-type epoxy resin, an alkyl-modified triphenol methane epoxyresin, a naphthalene-type epoxy resin, a dicyclopentadiene-type epoxyresin and a dicyclopentadiene-modified phenol-type epoxy resin, or amixture of at least two thereof may be used.

In an exemplary embodiment of the present application, the first layeror the second layer may include other components such as theabove-described active energy ray polymerizable compound, a radicalinitiator, a tackifier, a moisture scavenger, a moisture blocker, adispersant or a silane compound as well as the above-described resin,and the components of the first and second layers may be the same as ordifferent from each other. Also, the second layer may include a curablematerial, a curing agent, or a filler in a suitable range of contentdepending on a desired physical property. Meanwhile, the content of themoisture scavenger may be controlled depending on a damage of theelement by considering the fact that the encapsulation film is appliedin encapsulating the organic electronic element. For example, a smallamount of or no moisture scavenger may be included in the layer incontact with the element. In an exemplary embodiment, the second layerin contact with the element may include the moisture scavenger at 0 to20% of the total mass of the moisture scavenger contained in theencapsulation film. Also, the first layer not in contact with theelement may include the moisture scavenger at 80 to 100% of the totalmass of the moisture scavenger contained in the encapsulation film.

A sequence of stacking the second layer and the first layer additionallystacked is not particularly limited. For example, the second layer maybe formed on the first layer, or on the contrary, the first layer may beformed on the second layer. Also, the encapsulation film may be composedof three or more layers. For example, two or more of the first layersmay be included, or two or more of the second layers may be included.

In an exemplary embodiment, the first layer may have an elastic portioncalculated by General Equation 1 of 30 to 80%, and the second layer mayhave an elastic portion calculated by General Equation 2 of 8 to 40%.

Ep(unit:%)=100×σ2/σ1  [General Equation 2]

In General Equation 2, σ1 is the maximum stress value measured when 30%of stain is applied to the film by applying a normal force of about 200gf at 85° C. using a parallel plate having a diameter of 8 mm in astress relaxation test mode of an advanced rheometric expansion system(ARES) while the pressure-sensitive adhesive layer is formed to athickness of 600 μm, and σ2 is a stress value measured after the statein which the strain is applied to the film is maintained for 180seconds. Specifically, the pressure-sensitive adhesive layer is firstformed to a thickness of 600 μm, and a stress relaxation test mode ofthe advanced rheometric expansion system (ARES) is used. Here, a normalforce of about 200 gf is applied at 85° C. using a parallel plate havinga diameter of 8 mm. σ1 is the maximum stress value measured when 30% ofstrain is applied to the film, and σ2 is a stress value measured afterthe state in which the strain is applied to the film is maintained for180 seconds.

As described above, the encapsulation film may be applied to encapsulateor capsulate the OED such as an OLED. The encapsulation film exhibitingthe value (Ep) range may be formed in an encapsulating or capsulatingstructure with excellent durability without generating air bubbles undera high temperature durability test condition when applied to anencapsulation or capsulation process. In an exemplary embodiment, theencapsulation film may be used, as will be described later, to form theencapsulating or capsulating structure covering the top and sidesurfaces of an element of the OED.

The term “advanced rheometric expansion system (ARES)” is a rheometerevaluating viscoelastic properties such as viscosity, shear modulus,loss factor and storage modulus of a material. The instrument is amechanical measuring device that can apply dynamic and normal states toa sample and measure a transfer torque to an extent that the sample isresistant to the stress applied as described above.

In an exemplary embodiment, the encapsulation film of the presentapplication may be directly attached to a metal layer on the first layerof the pressure-sensitive adhesive layer. The term “directly attached”used herein may mean that there is no layer between two layers. Also,the second layer may be attached to a substrate on which an element isformed to entirely seal the element. That is, the second layer may bedirectly attached to the substrate.

In an exemplary embodiment, the value Ep calculated by General Equation2 as described above of the first layer of the exemplary encapsulationfilm may be 30 to 80%, 30 to 75% or 30 to 70%. Also, the value Epcalculated by General Equation 2 as described above of the second layermay be 8 to 40%, 10 to 40% or 20 to 40%. In the present application, theadhesive durability and reliability of the first layer may beexcellently maintained by controlling the Ep value within the aboverange by considering that the first layer is directly attached to themetal layer. Also, in the present application, the lamination qualitybetween the substrate and the encapsulation film of the second layer maybe achieved by controlling the Ep value within the above range. Thevalue of the elastic portion of the first layer according to the presentapplication may be the same as or higher than the value of the elasticportion of the second layer, but the present application is not limitedthereto.

In an exemplary embodiment of the present application, the first layermay have a probe tack force measured according to ASTM D2979 within arange of 50 to 500 gf, and specifically, the first layer may have aprobe tack force of 60 to 450 gf or 70 to 400 gf. Also, the second layermay have a probe tack force measured according to ASTM D2979 within arange of 3 to 100 gf, and specifically, the second layer may have aprobe tack force of 3 to 90 gf.

Also, while formed to a thickness of 100 μm, the pressure-sensitiveadhesive layer of the encapsulation film according to the presentapplication may have a water vapor transmission rate (WVTR) of 50, 40,30, 20 or 10 g/m²·day or less, which is measured in a thicknessdirection of the film at 100° F. and a relative humidity of 100%. As thecomposition or crosslinking condition of the pressure-sensitive adhesiveare adjusted to have such a WVTR, when the pressure-sensitive adhesiveis applied to the encapsulation or capsulation structure of theelectronic device, the encapsulation or capsulation structure mayeffectively block moisture or oxygen permeated from the outside and thusstably protect the element. As the WVTR is lower, a more excellentmoisture blocking property may be exhibited, and therefore, the lowerlimit may be, but is not particularly limited to, for example, 0g/m²·day.

In an exemplary embodiment of the present application, the encapsulationfilm may further include a metal layer. The metal layer according to anexemplary embodiment of the present application may be transparent oropaque. The metal layer may be formed by depositing metal on a thinmetal foil or a polymer base film. For the metal layer, any materialhaving thermal conductivity and a moisture blocking property may be usedwithout limitation. The metal layer may include any one of a metal, ametal oxide, a metal nitride, a metal carbide, a metal oxynitride, ametal oxyboride, and a blend thereof. For example, the metal layer mayinclude an alloy of two or more metals, for example, an iron-nickelalloy. Also, in one example, the metal layer may include a metal oxidesuch as silicon oxide, aluminum oxide, titanium oxide, indium oxide, tinoxide, tin indium oxide, tantalum oxide, zirconium oxide, niobium oxideor a blend thereof. The metal layer may be deposited using a means forelectrolysis, rolling, heated evaporation, electron beam evaporation,sputtering, reactive sputtering, chemical vapor deposition, plasmachemical vapor deposition or electron cyclotron resonance plasma sourcechemical vapor deposition. In one exemplary embodiment of the presentapplication, the metal layer may be deposited by reactive sputtering.

Preferably, the metal layer may have a thermal conductivity of 50 W/mKor more, 60 W/mK or more, 70 W/mK or more, 80 W/mK or more, 90 W/mK ormore, 100 W/mK or more, 110 W/mK or more, 120 W/mK or more, 130 W/mK ormore, 140 W/mK or more, 150 W/mK or more, 200 W/mK or more, or 250 W/mKor more. Due to the high thermal conductivity, heat generated at alaminating interface in a process of laminating the metal layer may bemore rapidly emitted. Also, because of the high thermal conductivity,heat accumulated in the operation of the OED may be quickly emitted toan outside, and thus a temperature of the OED itself may be maintainedlower, and cracks and defects may be reduced.

The term “thermal conductivity” used herein may be a degree of theability to transfer heat by conduction, and the unit may be W/mK. Theunit is a degree of heat transmission of a material at the sametemperature and distance, and refers to the unit (watt) of heat withrespect to the unit (meter) of a distance and the unit (kelvin) of atemperature.

The pressure-sensitive adhesive layer of the exemplary encapsulationfilm may satisfy General Equation 1 shown below. Also, theabove-described metal layer may be further included.

d≦1 mm  [General Equation 1]

In General Equation 1, d is a creeping distance of thepressure-sensitive adhesive layer creeped behind when a sample preparedby forming the pressure-sensitive adhesive layer having a thickness of50 μm on one surface of a metal base is attached to a glass in anadhesive area of 1 cm×1 cm, and 500 g of a weight is loaded to the metalbase at 85° C. for 1 hour. Here, the metal base may be formed of copper,aluminum, nickel, invar or stainless steel (SUS). In detail, the surfaceof the pressure-sensitive adhesive layer of the laminate sampleincluding the pressure-sensitive adhesive layer and the metal base maybe attached to the glass in an area of 1 cm×1 cm, and a weight may beloaded to the metal base as described above. The creeping distance ofthe pressure-sensitive adhesive layer may be measured in a distance ofthe movement of the metal base. In the general equation, d may be 1 mmor less, for example, 990 μm or less, 950 μm or less, 800 μm or less,700 μm or less, 600 μm or less, or 400 μm or less.

Also, in one example, the pressure-sensitive adhesive layer of theencapsulation film of the present application may have a Mooneyviscosity (η*) of 5000 to 10⁷ Pa·s measured by a shear stress using aplanar jig having a diameter of 8 mm at a strain of 5%, a frequency of 1Hz and any one temperature point in the range of 30 to 150° C. TheMooney viscosity may be measured by a known method, for example, an ARES(TA). The range of the viscosity may be, for example, 5,000 to 10⁷ Pa·s,5,000 to 10⁶ Pa·s or 5,000 to 5×10⁵ Pa·s. The metal layer may be furtherincluded on one surface of the pressure-sensitive adhesive layersatisfying the viscosity range. The pressure-sensitive adhesive layersatisfying the viscosity range may include the above-described compoundof Formula 1 or active energy ray polymerizable compound.

The encapsulation film may further include a base film or release film(hereinafter, probably referred to as a “first film”), and have astructure in which the pressure-sensitive adhesive is formed on the baseor release film. Also, the structure may further include a base orrelease film formed on the pressure-sensitive adhesive (hereinafter,also referred to as a “second film”).

FIGS. 1 and 2 are cross-sectional views of an encapsulation filmaccording to an exemplary embodiment of the present application.

As shown in FIG. 1, the encapsulation film of the present applicationmay include a pressure-sensitive adhesive layer 12 and a metal layer 13,which are formed on a base film or release film 11. Also, FIG. 2 showsthe pressure-sensitive adhesive layer 12 including a first layer 12 aand a second layer 12 b.

A specific type of the first film capable of being used in the presentapplication is not particularly limited. In the present application, asthe first film, for example, a general polymer film used in the art maybe used. In the present application, for example, as the base or releasefilm, a polyethyleneterephthalate film, a polytetrafluoroethylene film,a polyethylene film, a polypropylene film, a polybutene film, apolybutadiene film, a vinyl chloride copolymer film, a polyurethanefilm, an ethylene-vinyl acetate film, an ethylene-propylene copolymerfilm, an ethylene-acrylic acid ethyl copolymer film, an ethylene-acrylicacid methyl copolymer film or a polyimide film may be used. Also, one orboth surfaces of the base film or release film of the presentapplication may be treated with a suitable releasing treatment. As anexample of a releasing agent used for the releasing treatment of thebase film, an alkyde-, silicon-, fluorine-, unsaturated ester-,polyolefin- or wax-based agent may be used, and for the thermalresistance, an alkyde-, silicon- or fluorine-based releasing agent maybe used, but the present application is not limited thereto.

In the present application, the thickness of the base film or releasefilm (the first film) is not particularly limited, and may be suitablyselected according to use. For example, in the present application, thethickness of the first film may be about 10 to 500 μm, and preferablyabout 20 to 200 μm. When the thickness is less than 10 μm, the base filmmay be easily deformed in the manufacturing process, and when thethickness is more than 500 μm, economic feasibility is reduced.

A thickness of the pressure-sensitive adhesive layer included in theencapsulation film of the present application is not particularlylimited, and may be suitably selected according to the followingcondition by considering the use of the film. The thickness of thepressure-sensitive adhesive layer may be about 5 to 200 μm, andpreferably about 5 to 100 μm. When the thickness of thepressure-sensitive adhesive layer is less than 5 μm, a sufficientadhesive property may not be ensured, and a rate of the loss of amoisture blocking ability during the process may be increased. When thethickness is more than 200 μm, it is difficult to ensure processability,a space exposed to the side surface may expand so that the moistureblocking property may be degraded, the thermal resistance may bedegraded, and the economic feasibility may be deceased.

The present application also relates to a method of manufacturing anencapsulation film. The exemplary encapsulation film may be manufacturedby molding the pressure-sensitive adhesive layer in a film or sheetshape.

In an exemplary embodiment, the method may include applying a coatingsolution including a component constituting the above-describedpressure-sensitive adhesive layer to a base or release film in a sheetor film shape, and drying the applied coating solution.

The coating solution may be prepared by dissolving or dispersing thecomponent of each pressure-sensitive adhesive layer described above in asuitable solvent. In an exemplary embodiment, the pressure-sensitiveadhesive layer may be prepared by dissolving or dispersing the moisturescavenger or filler in a solvent when needed, and mixing the moisturescavenger or filler with an encapsulation resin after grinding.

A type of the solvent used in the preparation of the coating solution isnot particularly limited. However, when a dry time of the solvent is toomuch longer or drying at a high temperature is needed, problems in termsof workability or durability of the encapsulation film may occur, andtherefore a solvent having a volatile temperature of 150° C. or less maybe used. In consideration of film moldability, a small amount of asolvent having the above range or more of a volatilizing temperature maybe mixed. As the solvent, one or two or more of methylethylketone (MEK),acetone, toluene, dimethylformamide (DMF), methylcellosolve (MCS),tetrahydrofuran (THF), xylene and N-methylpyrrolidone (NMP) may be used,but the present application is not limited thereto.

A method of applying the coating solution to the base or release film isnot particularly limited, and thus may be, for example, a known coatingmethod such as knife coating, roll coating, spray coating, gravurecoating, curtain coating, comma coating or lip coating.

The applied coating solution is dried, the solvent is volatilized, andthus a pressure-sensitive adhesive layer may be formed. The drying maybe performed, for example, at 70 to 150° C. for 1 to 10 minutes. Thedrying condition may be changed by considering the used solvent.

A method of stacking a first layer and a second layer is notparticularly limited. For example, the first layer and the second layer,which are formed on respective release films, may be laminated, therebyforming a multi-layered encapsulation film, or the second layer may beformed directly on the first layer and vice versa.

After drying, a metal layer may be formed on the pressure-sensitiveadhesive layer. A method of forming the metal layer may be a techniqueknown in the art. For example, the metal layer may be formed of metalfoil, or formed by depositing a metal on a polymer base. For example,the metal layer may be formed by electrolysis or rolling.

The present application also relates to an OED. The OED may include asubstrate; an organic electronic element formed on the substrate; and anencapsulation film encapsulating entire surfaces, for example, all ofthe top and side surfaces of the organic electronic element. Theencapsulation film may include a pressure-sensitive adhesive layercontaining a pressure-sensitive adhesive composition in a crosslinkedstate. Also, the encapsulation film may further include a metal layerformed on the pressure-sensitive adhesive layer.

Here, the organic electronic element may be, for example, an organiclight emitting element.

Also, the present application relates to a method of manufacturing anOED. The OED may be manufactured using, for example, the encapsulationfilm.

The pressure-sensitive adhesive layer may be formed for a structureexhibiting an excellent moisture blocking property in the OED, andeffectively fixing and supporting the substrate and the metal layer.

In addition, the pressure-sensitive adhesive layer may be formed to bestable regardless of a type of the OED, for example, a top emission orbottom emission type.

The term “pressure-sensitive adhesive layer” used herein may be apressure-sensitive adhesive covering all of the top and side surfaces ofthe organic electronic element.

FIG. 3 is a schematic diagram of an exemplary OED, in which an organicelectronic element is an organic light emitting element.

To manufacture the OED, for example, applying the above-describedencapsulation film to the substrate on which the organic electronicelement is formed to cover the entire surfaces of the organic electronicelement; and curing the encapsulation film may be used.

The term “curing” used herein may refer to preparation of apressure-sensitive adhesive by crosslinking the pressure-sensitiveadhesive composition of the present application through heating or UVirradiation.

In detail, the organic electronic element may be formed by forming atransparent electrode on a glass or polymer film used as a substratethrough vacuum deposition or sputtering, forming a light emittingorganic material layer, for example, consisting of a hole transportlayer, an emitting layer and an electron transport layer on thetransparent electrode, and further forming an electrode layer thereon.Subsequently, the pressure-sensitive adhesive layer of the encapsulationfilm is disposed to cover the entire surfaces of the organic electronicelement of the substrate, which has gone through the above-describedprocess.

In an exemplary embodiment, as shown in FIG. 3, a product forencapsulating an OED may be disposed such that the pressure-sensitiveadhesive layer 12 of the encapsulation film is disposed to be in contactwith an OED 22 and a substrate 21. Also, the metal layer 13 may bedisposed on the pressure-sensitive adhesive layer 12.

Effect

The present application provides a pressure-sensitive adhesivecomposition, which can form a structure for effectively blockingmoisture or oxygen entering an OED from the outside and has an excellentheat retention under a high-temperature and high-humidity condition, andan encapsulation film including the same.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are cross-sectional views of an encapsulation filmaccording to an exemplary embodiment of the present application; and

FIG. 3 is a cross-sectional view of an OED according to an exemplaryembodiment of the present application.

EXPLANATION OF REFERENCE NUMERALS

-   -   11: base film or release film    -   12: pressure-sensitive adhesive layer    -   12 a: first layer    -   12 b: second layer    -   13: metal layer    -   21: substrate    -   22: organic electronic device

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, the present application will be described in further detailwith reference to examples according to the present application andcomparative examples not according to the present application, and thescope of the present application is not limited to the examples asfollows.

Example 1

A coating solution was prepared by adding 50 g of butyl rubber (Br068,EXXON) as a polymer derived from butylene, 24 g of a hydrogenatedhydrocarbon resin (Eastotac H-100L) as a tackifier, 15 g of amonofunctional acrylate, i.e., 2-(2-ethoxyethoxy)ethyl acrylate as thecompound of Formula 1, 10 g of trimethylolpropane triacrylate as amultifunctional active energy ray polymerizable compound and 1 g of2,2-dimethoxy-1,2-diphenylethane-1-one (Irgacure 651, Ciba) as a radicalinitiator, and diluting the resultant mixture with toluene to have asolid content of about 15 wt %.

An encapsulation film was formed by forming a pressure-sensitiveadhesive layer to a thickness of 50 μm by coating a release surface of arelease PET with the prepared solution and drying the coated product inan oven at 100° C. for 15 minutes, and laminating the pressure-sensitiveadhesive layer with a copper film having a thickness of 20 μm. Physicalproperties of the film sample irradiated with UV rays at 2 J/cm² weremeasured.

Example 2

An encapsulation film was formed by the same method as described inExample 1, except that the compound of Formula 1 was replaced withstearyl acrylate.

Example 3

An encapsulation film was formed by the same method as described inExample 1, except that the compound of Formula 1 was replaced withlauryl acrylate.

Example 4

An encapsulation film was formed by the same method as described inExample 1, except that the compound of Formula 1 was replaced withisodecyl acrylate.

Comparative Example 1

An encapsulation film was formed by the same method as described inExample 1, except that the compound of Formula 1 was not included.

Comparative Example 2

An encapsulation film was formed by the same method as described inExample 1, except that the compound of Formula 1 was replaced withlauryl methacrylate.

Comparative Example 3

An encapsulation film was formed by the same method as described inExample 1, except that the compound of Formula 1 was replaced withisobornyl acrylate.

Experimental Example 1 Non-Lamination of Panel

The pressure-sensitive adhesive layer having a thickness of 50 μm and asize of 14 cm×9 cm, which was formed in any one of Examples andComparative Examples, was attached to the center of a 0.7 T glass havinga size of 150 cm×10 cm using a roll laminator. A glass having the samesize as the prepared specimen was laminated through vertical pressingusing a vacuum laminator at 25 to 100° C. and a vacuum degree of 100 paunder a pressure of 0.5 MPa. A laminating property was determined by thedegree of non-lamination or bubble generation on the entire surfaces ofa pressure-sensitive adhesive, and thus when non-lamination orgeneration of at least one bubble having a diameter of 3 mm or moreoccurred, it was determined as a lamination failure.

Experimental Example 2 Creeping Distance

A sample prepared by forming the pressure-sensitive adhesive layerprepared in any one of Examples and Comparative Examples on one surfaceof a metal base having a thickness of 50 μm was attached to a glass atan adhesive area of 1 cm×1 cm, 500 g of a weight was loaded to the metalbase in a gravity direction at 85° C. for 1 hour, and then a creepingdistance of the pressure-sensitive adhesive layer was measured. Here, asthe metal base, copper was used. When the weight was loaded, the case inwhich the adhesive area was all creeped, the thus the sample wasdetached was determined as a failure.

TABLE 1 85° C. retention, creeping Lamination or non- distance (μm)lamination of panel Example 1  0 X Example 2 960 X Example 3 500 XExample 4 100 X Comparative failed Lamination failed Example 1Comparative failed X Example 2 Comparative failed Lamination failedExample 3

Since Comparative Examples 1 and 3 did not include the compound ofFormula 1, it is shown that the heat retention is decreased at hightemperature, and panel lamination is failed. Also, in ComparativeExample 2, lauryl methacrylate is included in the pressure-sensitiveadhesive composition, and a UV curing rate is delayed due to a sterichindrance effect of a methyl group, resulting in degradation of thermalresistance.

What is claimed is:
 1. A pressure-sensitive adhesive composition,comprising: a polymer derived from butylene; and a compound satisfyingFormula 1,

where T is a linear or branched alkyl group, alkenyl group or alkynylgroup having 6 to 30 carbon atoms, or —U—[O—W]—O-Q, in which U and W areeach independently an alkylene group or alkylidene group, Q is an alkylgroup, alkenyl group, alkynyl group or aryl group, and n is a numberfrom 0 to
 10. 2. The composition of claim 1, wherein the polymer derivedfrom butylene is a homopolymer of a butylene monomer; a copolymercopolymerizing a butylene monomer with a different monomer capable ofbeing polymerized therewith; a reactive oligomer using a butylenemonomer; or a mixture thereof.
 3. The composition of claim 2, whereinthe monomer capable of being polymerized with the butylene monomer isisoprene, styrene or butadiene.
 4. The composition of claim 2, whereinthe reactive oligomer using the butylene monomer comprises a butylenepolymer having a reactive functional group, and the butylene polymerbinds to a different polymer having a reactive functional group.
 5. Thecomposition of claim 1, wherein the polymer derived from butylene iscomprised at 60 to 95 parts by weight, and the compound satisfyingFormula 1 is comprised at 5 to 40 parts by weight.
 6. The composition ofclaim 1, further comprising: a multifunctional active energy raypolymerizable compound satisfying Formula 2,

where R₁ is hydrogen or an alkyl group having 1 to 4 carbon atoms, n isan integer of 2 or higher, and X is a residue derived from a linear,branched or cyclic alkyl group having 3 to 30 carbon atoms.
 7. Thecomposition of claim 6, wherein the polymer derived from butylene iscomprised at 50 to 90 parts by weight, the compound satisfying Formula 1is comprised at 5 to 35 parts by weight, and the multifunctional activeenergy ray polymerizable compound of Formula 2 is comprised at 5 to 25parts by weight.
 8. The composition of claim 1, further comprising: atackifier.
 9. The composition of claim 8, wherein the tackifier is ahydrogenated cyclic olefin-based polymer.
 10. The composition of claim8, wherein the tackifier is comprised at 5 to 100 parts by weight withrespect to 100 parts by weight of the polymer.
 11. The composition ofclaim 1, further comprising: a radical initiator.
 12. The composition ofclaim 11, wherein the radical initiator is a photoinitiator or thermalinitiator.
 13. The composition of claim 1, further comprising: amoisture scavenger.
 14. An encapsulation film, comprising: apressure-sensitive adhesive layer which comprises the pressure-sensitiveadhesive composition of claim 1 or a crosslinked product thereof. 15.The film of claim 14, wherein the pressure-sensitive adhesive layercomprises a second layer comprising the pressure-sensitive adhesivecomposition of claim 1 or a crosslinked product thereof and a firstlayer comprising a pressure-sensitive adhesive resin or an adhesiveresin.
 16. The film of claim 14, further comprising: a metal layerformed on one surface of the pressure-sensitive adhesive layer.
 17. Thefilm of claim 16, wherein the metal layer has a thermal conductivity of50 W/mK or more.
 18. The film of claim 14, wherein thepressure-sensitive adhesive layer has a water vapor transmission rate(WVTR) in a thickness direction of 50 g/m²·day or less, while formed toa thickness of 100 μm.
 19. An organic electronic device, comprising: asubstrate; an organic electronic element formed on the substrate; andthe encapsulation film of claim 14, which encapsulates the entiresurfaces of the organic electronic element.
 20. A method ofmanufacturing an organic electronic device, comprising: applying theencapsulation film of claim 14 to a substrate on which an organicelectronic element is formed to cover the entire surfaces of the organicelectronic element; and curing the encapsulation film.